U.S. Pat. No. 5,150,967, issued Sep. 29, 1992, discloses a milk shake machine for mixing thick, hard ice cream shakes. The machine incorporates a housing to which a container is locked and sealed, the container being in a suspended, elevated condition. Two gear motors are disposed within the housing, one employed to rotate a shaft and mixing head and the other to move the mixing head vertically within the container.
Also known in the prior art are conventional milk shake machines consisting of an electric motor, shaft, and mixing disc. The device is supported on a stand or hangs from a wall bracket. When one wishes to make a hard ice cream milk shake, a metal cup is manually held under the revolving shaft and disc while the cup is manually manipulated vertically and in a stirring motion. This method is time consuming and inefficient and may even introduce foreign matter into the mixture as a result of the mixing head coming into contact with the sides of the metal cup.
While the milk shake machine disclosed in U.S. Pat. No. 5,150,967 has a number of advantages over the conventional prior art milk shake machines, it too has certain deficiencies, not the least of which is the fact that the cup or receptacle is not positively supported on its bottom, but rather is suspended from its upper end in mid air. This approach can result in spillage if the user does not properly connect the receptacle to the housing. Some difficulties may also arise with respect to cleaning of the housing structure at the point of attachment of the container or receptacle to the housing.